Dear Pavani,

To calculate the GST activity such as other enzymes with extinction coefficient, at first you use below formula to obtain product concentration;

OD = ε х C х  L

OD = Optical Density of your sample (the number that output of microplate reader or Spectrophotometer)

ε  = Extinction Coefficient

C = Product Concentration (μmol/ml)

L = Lightpath length of Cuvette (or depth of the well in a microplate that related to sample volume in it)

With this formula, you can gain the Product Concentration.

In the next step by using below formula, you can obtain specific activity for Glutathione-S-Transferase and other enzymes;

Final reaction Volume (ml) х Product Concentration (μmol/ml) / Enzyme Extract Volume (ml) х Time (minute) х Protein Concentration of Enzyme Extract (mg/ml)

Then you can report your results in U per ml (Unit activity/ml), which means in a certain concentration of protein, your enzyme activity is ... .

Kind regards, Homayoon.

Following paper might help you..

Thank you Andrey Massarsky and Kavita Rana

@ Andrey Massarsky could you please give me equation form to calculate the activity ?

My worked have assay GST by serum reduce glutathione and Malone dialdihyde by ELISA kit to mesurement concentration

Dear Pavani,

To calculate the GST activity such as other enzymes with extinction coefficient, at first you use below formula to obtain product concentration;

OD = ε х C х  L

OD = Optical Density of your sample (the number that output of microplate reader or Spectrophotometer)

ε  = Extinction Coefficient

C = Product Concentration (μmol/ml)

L = Lightpath length of Cuvette (or depth of the well in a microplate that related to sample volume in it)

With this formula, you can gain the Product Concentration.

In the next step by using below formula, you can obtain specific activity for Glutathione-S-Transferase and other enzymes;

Final reaction Volume (ml) х Product Concentration (μmol/ml) / Enzyme Extract Volume (ml) х Time (minute) х Protein Concentration of Enzyme Extract (mg/ml)

Then you can report your results in U per ml (Unit activity/ml), which means in a certain concentration of protein, your enzyme activity is ... .

Kind regards, Homayoon.

Thank you Mohammad Homayoonzadeh